Branched aromatic carbonate polymers have been well known for many years. The branching agents employed are tri-functional or higher molecules which can incorporate within a linear aromatic carbonate polymer chain and have a functional group left for further reaction which provides the branched molecule. Various branching agents have been utilized in polycarbonate to prepare a branched polycarbonate. One of the latest being used is the compound 1,1,1-tris-(4-hydroxyphenyl)ethane.
The utilities for these branched polycarbonates are generally well known and are characterized by their increased melt strength. Such utilities include film, fibers, sheets, tubes, rods and in particular blow molding applications such as bottles and various containers. The previously mentioned compound, abbreviated hereafter as THPE, was used to replace tri mellitic trichloride (TMTC). The latter compound has been used as a branching agent in polycarbonate for many years. However it had the inherent problem of having poor stability to ultra violet radiation. The UV stability of the branched polycarbonate having the THPE therein was substantially increased. However an unforeseen problem was noted in the blow molding application of bottles. The previous branched polycarbonate utilizing the "TMTC" compound had provided excellent materials for the actual bottle application. However the branched polycarbonate with the new compound, THPE, was having serious problems in the field, even though it should have behaved very similarly to its predecessor branched polycarbonate. Specifically in making one gallon containers with branched bisphenol-A polycarbonate utilizing 0.40 mole percent THPE, based on the moles of bisphenol-A present in the polycarbonate, the branched polycarbonate did not process up to performance specifications arrived at using the earlier commercial TMTC branched bisphenol-A polycarbonates. Problems such as entrapped bubbles in the bottles, haze due to flow lines, as well as irregular parisons were observed.
A new formulation was devised to overcome these problems. This formulation utilized a smaller amount THPE. Such formulation did not encounter the previously observed problems with the higher portion of THPE.